A) Field of the Invention
The present invention relates to a semiconductor device manufacture method and a semiconductor device, and more particularly to a manufacture method for a semiconductor device having plugs and wirings made of copper or copper alloy and a semiconductor device of this kind.
B) Description of the Related Art
Copper (Cu) is used as the material of wirings of a semiconductor integrated circuit device. As compared to conventionally used aluminum (Al), copper is likely to diffuse into an insulating film and short circuit occurs easily. Further, a copper film has insufficient adhesion to an insulating film and is likely to be peeled off during a chemical mechanical polishing (CMP) process or the like. Furthermore, copper is likely to be oxidized more than Al. In addition, since a copper oxide film does not suppress diffusion of oxidizing molecules, oxidation advances easily.
In order to prevent copper diffusion and improve tight adhesion to an insulating film, a structure has been adopted in which a barrier metal layer made of Ti, TiN, Ta, TaN, W, WN or the like is inserted between a copper wiring and an insulating film. The material of the barrier metal layer has a higher electric resistivity than copper. As a barrier metal layer is formed on the inner wall of a via hole, particularly a small diameter via hole, a ratio occupied by the barrier metal layer in a plan cross section becomes high and the resistance increases. If a barrier metal layer is made thin to suppress an increase in resistance, it is difficult to maintain a sufficient barrier performance.
Methods of forming a copper wiring which solves the above-described problems are disclosed in Japanese Patent Publication HEI-7-60852 and Japanese Patent Laid-open Publication HEI-11-54458. According to the method disclosed in Publication HEI-7-60852, copper alloy is embedded in a wiring trench formed in an interlayer insulating film. Heat treatment is performed to react an alloy element in the copper alloy with oxygen in the insulating film to form a metal oxide film. This metal oxide film has functions to prevent copper diffusion and improve adhesion. Al or Cr is used as the alloy element.
According to the method disclosed in Laid-open Publication HEI-11-54458, a thin copper alloy layer is formed in a wiring trench and then pure copper is embedded in the wiring trench. Heat treatment is performed to react an alloy element in the copper alloy with oxygen in the insulating film to form a metal oxide film. This metal oxide film has functions to prevent copper diffusion and improve adhesion. Mg, Al, B, Ta, Te, Ti or the like is used as the alloy element.